Police placed undercover agent Parisi in a jail cellblock with respondent Perkins, who was incarcerated on charges unrelated to the murder that Parisi was investigating. When Parisi asked him if he had ever killed anybody, Perkins made statements implicating himself in the murder. He was then charged with the murder. The trial court granted respondent's motion to suppress his statements on the ground that Parisi had not given him the warnings required by Miranda v. Arizona,384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed.2d 694, before their conversations. The Appellate Court of Illinois affirmed, holding that Miranda prohibits all undercover contacts with incarcerated suspects that are reasonably likely to elicit an incriminating response.

Held: An undercover law enforcement officer posing as a fellow inmate need not give Miranda warnings to an incarcerated suspect before asking questions that may elicit an incriminating response. The Miranda doctrine must be enforced strictly, but only in situations where the concerns underlying that decision are present. Those concerns are not implicated here, since the essential ingredients of a "police-dominated atmosphere" and compulsion are lacking. It is Miranda's premise that the danger of coercion results from the interaction of custody and official interrogation, whereby the suspect may feel compelled to speak by the fear of reprisal for remaining silent or in the hope of more lenient treatment should he confess. That coercive atmosphere is not present when an incarcerated person speaks freely to someone whom he believes to be a fellow inmate and whom he assumes is not an officer having official power over him. In such circumstances, Miranda does not forbid mere strategic deception by taking advantage of a suspect's misplaced trust. The only difference between this case and Hoffa v. United States,385 U.S. 293, 87 S.Ct. 408, 17 L.Ed.2d 374-which upheld the placing of an undercover agent near a suspect in order to gather incriminating information-is that Perkins was incarcerated. Detention, however, whether or not for the crime in question, does not warrant a presumption that such use of an undercover agent renders involuntary the incarcerated suspect's resulting confession. Mathis v. United States,391 U.S. 1, 88 S.Ct. 1503, 20 L.Ed.2d 381-which held that an inmate's statements to a known agent were inadmissible because no Miranda warnings were given-is distinguishable. Where the suspect does not know that he is speaking to a government agent, there is no reason to assume the possibility of coercion. Massiah v. United States,377 U.S. 201, 84 S.Ct. 1199, 12 L.Ed.2d 246, and similar cases which held that the government may not use an undercover agent to circumvent the Sixth Amendment right to counsel once a suspect has been charged-are inapplicable, since, here, no murder charges had been filed at the time of interrogation. Also unavailing is Perkins' argument that a bright-line rule for the application of Miranda is desirable, since law enforcement officers will have little difficulty applying the holding of this case. Pp. 296-300.